1. Field of the Invention
This invention relates to the art of electronic switching systems for power supplies of lamps, motors and other power consuming devices, and more particularly concerns an adapter connectable to an external power supply and including an automatic switching circuit interposed between the power supply and power consuming devices, such as lamps mountable on the adapter, to keep at least one of a pair of primary and standby power consuming devices operating at all times.
2. Description of the Prior Art
Industrial plants, hospitals, public buildings, theaters, bridges, highways, tunnels, airports, etc. . . often have certain electrical lighting fixtures on which is mounted a lamp which must be operating at all times. If the lamp fails to operate, a serious safety hazard is created. This situation has been recognized heretofore. One conventional expedient to remedy the situation is to provide a critical lighting fixture with two or more lamps, so that at least one lamp is operating even though others fail. This expedient has several disadvantages and objections. The most obvious being the high maintenance cost in both lamp bulbs and manpower to replace same. In addition, very often these lamp fixtures are unattended, so that all lamps can burn out to create a hazardous condition. Another objection is that in an installation where only one lamp is required, an excessive amount of power is consumed by burning two or more lamps at the same time. Many of these critical lighting fixtures are located on high ceilings or in other places difficult to reach, so that an appreciable interval of time may elapse before all inoperative lamps may be replaced. This situation undesirably prolongs the hazardous condition in an installation where no lamps are operating and at least one lamp must be operating at all times.